1. Field of Use
This invention relates generally to a connecting rod in the drive connection between a crank shaft and a piston in a gas compressor or the like.
In particular, it relates to the construction of a two-piece bearing assembly employed in a crank pin receiving hole in the connecting rod.
2. Description of the Prior Art
U.S. Pat. No. 4,567,815, issued Feb. 4, 1986, to Erich J. Kocher for "Connecting Rod And Bearing Assembly Therefor" and assigned to the same assignee as the present invention, discloses a piston, crankshaft and connecting rod arrangement for a refrigeration gas compressor which is identical to that disclosed herein.
That patent discloses a connecting rod which comprises a wrist pin hole at one end and a cylindrical crank pin hole at its other end. The upper surface of the crank pin hole is provided with an oil receiving groove which communicates with an oil passage extending through the connecting rod to the wrist pin hole. The crank pin hole in the connecting rod is adapted to receive the crank pin and the connecting rod bearing assembly disposed therearound. The crank pin comprises a first oil passage which extends axially therethrough and a second oil passage which extends transversely through the crank pin and communicates with the first oil passage.
The connecting rod bearing assembly comprises two (upper and lower) semi-circular bearing sections. The upper bearing section has a smooth inner bearing surface with two wedge-shaped oil well recesses (i.e., of generally triangular cross-sectional configuration) formed therein at opposite ends thereof and has two oil feed holes extending through the oil well recess, one near each end of the oil well recess. The lower bearing section has an inner bearing surface with an oil-receiving groove formed in and circumferentially extending along its inner surface between opposite ends of the lower bearing section. The ends of the groove in the lower bearing section communicate with the oil well recesses in the upper bearing section and continuously supply oil to the oil well recesses and oil feed holes therein.
During operation, the upper bearing section and the confronting crank pin surface are subjected to heavy loads on each upward compression stroke of the crank pin. However, the overall construction of the connecting rod, crank pin and connecting rod bearing assembly avoids wear on the crank pin and bearing assembly by providing hydrodynamic lubrication of the bearing assembly. Lubricating oil is fed under pressure through the first and second passages in the crank pin and is expelled from opposite ends of the second passage. Depending on the position of the crank pin relative to the bearing assembly, oil flows directly to the two oil well recesses in the upper section or to the groove in the lower bearing section and then to the oil well recesses. From these recesses oil flows to the groove in the lower section and through the two oil feed holes in the upper bearing section. Oil flows through the two oil feed holes to the oil receiving groove in the connecting rod and from thence through the associated oil passage to the wrist pin hole.
On the compression stroke oil is drawn from one of the two oil well recesses in the upper bearing section hydrodynamically between the smooth inside load-bearing surface of the upper bearing section and the confronting surface of the crank pin. Oil also is forced from the groove in the lower bearing section between the two smooth inside load-bearing surfaces of the lower bearing section and the crank pin.
The oil well recesses at each end of the upper bearing section are continuously supplied with oil from the groove in the lower bearing section which is in communication at all times with the oil supply ports of the transverse oil passage in the crank pin.
While the bearing assembly disclosed and claimed in U.S. Pat. No. 4,567,815 has been used successfully and has excellent lubrication characteristics, it permits a relatively large amount of lubricating oil to be pumped into and through the bearing assembly and to spray from the bearings to other internal parts. This excessive quantity of lubricating oil needs to be pumped, cooled in the oil coolers and recovered and this detracts from overall system efficiency. The large amount of oil spray from the bearings also increases the possibility of oil pumping past the piston rings into the compression chamber.